1. Field of the Invention
The present invention relates to various semiconductor devices that use a capacitor or gate insulating film as a high relative dielectric constant insulating film, and a method of manufacturing the same.
2. Description of the Related Art
Recently, a capacitor insulating film and a gate insulating film are thinned more and more with high density of a LSI. In order to prevent a leak current from increasing with the foregoing thinning, a three-dimensional structure is changed, and thereby, the way to solve the problem is found. On the other hand, a high relative dielectric constant insulating film is used, and thereby, a physical film thickness is increased to prevent an increase of the leak current.
In particular, an inter-poly dielectric film (inter-electrode insulating film) is formed between a charge storage layer and a control gate electrode in a non-volatile semiconductor memory device such as flash memory. For example, an ONO film (three-layer stacked film, that is, silicon oxide film/silicon nitride film/silicon oxide film) is used as the foregoing inter-poly dielectric film. By doing so, a relative dielectric constant is improved, and three-dimensional structure is employed. However, the distance between cells is reduced; for this reason, interference between neighboring cells remarkably increases, and this is a factor of worsening device characteristics. As a result, there is a problem that it is difficult to employ the three-dimensional structure to increase an area.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2003-7861 discloses the following technique in order to realize a next-generation non-volatile semiconductor memory device. According to the technique, a high relative dielectric constant insulating film having a relative dielectric constant ∈r larger than conventionally is used as the inter-poly dielectric film. Specifically, the relative dielectric constant ∈r is larger than a relative dielectric constant ∈r=3.8 to 4 of the conventionally used silicon oxide film (SiO2 film). The foregoing high relative dielectric constant insulating film is used, and thereby, a capacity is made large without increasing the area. Therefore, there is no need of giving the three-dimensional structure, so that the manufacturing process is simplified. As a result, an element has high performance, and the method of manufacturing the device is made easy; therefore, a manufacturing process having high yield is realized.
A composite oxide such as hafnium aluminate (HfxAL1-xOy) is used as the foregoing high relative dielectric constant insulating film. The high relative dielectric constant insulating film is formed via a CVD process such as ALD process resulting from the following reasons of uniformity, mass production and low damage.
The following problem arises if the foregoing film is used as an inter-electrode insulating film of a semiconductor memory device, in particular, non-volatile semiconductor memory device. In this case, an applied electric filed is high; for this reason, leak current is not sufficiently restricted.
In the foregoing description, a problem in the prior art is described giving the inter-electrode insulating film of the non-volatile semiconductor memory device. In this case, the problem of the leak current of the high relative dielectric constant insulating film is not limited to the non-volatile semiconductor memory device. The same problem arises in the case of using the high relative dielectric constant insulating film as a capacitor insulating film of a storage (accumulation) capacitor. Further, the same problem exists in various insulating gate transistors employing a MOS capacitor using the high relative dielectric constant insulating film as the capacitor insulating film. Furthermore, the same leak current problem by high electric field exists in the following insulating gate transistors. One is an insulating gate transistor used as super high-speed switching element for logic integrated circuits. Another is an insulating gate transistor operating in a high frequency band such as terahertz. In particular, in an insulating gate transistor having a gate length of about 60 nm or less, the field strength of the high relative dielectric constant insulating film used as a gate insulating film becomes large. As a result, the leak current by high electric filed becomes a big problem.